(1) Field of the Invention
The present invention relates generally to filters and, more particularly, to a disposable filter for removing particulate matter from an aqueous flow, especially radioactive materials entrained in cooling water, which provides an improved cartridge-style filter for use in such installations to reduce the volume and weight of the hazardous waste resulting from the end of life of the filter.
(2) Description of the Prior Art
Nuclear reactors use water in primary and secondary support systems. Some of the particulate entrained in these systems are radioactive. These radioactive particles must be removed for safe and efficient system operational and maintenance. This is done conventionally by filter elements that are installed for a given period of time to remove the particulates. After a period of time, the filter becomes clogged with removed particulate and must be replaced.
Conventional filters for this purpose have a perforated, stainless steel outer cylinder and, in some cases, an inner stainless steel cylinder, and stainless steel end fittings, and a permanently installed interior filter medium. The filtrate flows from inside to outside through the filter medium and the pores of the stainless steel cylinder. The outer stainless steel cylinder and end fittings have been considered a necessity to give the filter the structural strength and integrity to withstand the temperature, pressure and dynamic filtration loads of the forces of the flowing liquid and avoid corrosion.
However, when the filter is spent, the outer and inner cylinders and end fittings become a large, strong, corrosion resistant, heavy piece of hazardous, radioactive waste. Requirements for disposal of this type of waste safely are very costly. The steel is difficult to compress to a reduced volume and does not easily shred to smaller pieces. Disposal of the filter, therefore, requires a great deal of cost.
One solution to this problem is disclosed in U.S. Pat. Nos. 5,478,469 and 5,678,230, issued to Bryan and Pop. These patents disclose a disposable filter for removing hazardous particulate matter from an aqueous flow. The filter includes a rigid support housing having an input port for the aqueous flow, an exit port for the aqueous flow, a brace to securingly engage a filter vessel for the aqueous flow, an internal seal and an external seal, and a disposable filter cartridge configured similarly to the housing and sized to be substantially entirely received within the housing and sealingly engage the internal seal and having a filter medium that extends across a path from the input port to the exit port when received in the housing, the cartridge having a terminal seal located to sealingly engage the cartridge to the aqueous flow filter vessel outside of the housing when the cartridge sealing engages with the internal seal. The rigid support housing may be installed in a filter vessel for an extended period and held in place by the brace, and repeatedly during the extended period, a disposable cartridge may be installed within the housing to seal the cartridge to the filter vessel, aqueous flow may be directed through the filter medium, and the cartridge may be removed and discarded. These patents are hereby incorporated by reference in their entirety.
For all of its advantages, the Bryan and Pop filter did have some drawbacks. Specifically, the brace arrangement was difficult to machine and install in the field. Furthermore, the disposable filter included some hard to dispose of metal parts. Finally, the porous outer sleeve used to add strength to the disposable filter took up critical space that limited the applications which could benefit from the filter.
Thus, there remains a need for a new and improved disposable filter which performs well in existing facilities, reduces the cost of disposal of spent filters contaminated with hazardous materials such as radioactive particulate matter while, at the same time, overcomes the problems associated with Bryan and Pop.